Hey everyone,On my bike's seat tube, there's the blue/red/black/yellow/green (flag/stripes). I also see them alot throughout the cycling culture. I was wondering what is the origin of it or the meaning to it ?

It's the world champion colors - you'll also see it in the VeloNation logo as well, albeit subtle.

You can see the back of Paolo Bettini when he was world champ here: http://www.velonation.com/News/ID/1687/Bettini-heads-to-Mendrisio.aspx

All former world champions earn the right to have the rainbow stripes on their sleeve - you can see it in the photo of Tom Boonen: http://www.velonation.com/News/ID/1930/Boonen-picked-wrong-wheel-to-follow.aspx